1. Field of the Invention
The present invention relates to an image pickup apparatus using a solid state image pickup device.
2. Related Background Art
A conventional MOS image pickup device used in a single CCD area array type camera is constructed as shown in FIG. 1. In FIG. 1, PE represents a photocell, PS a cell selection switch, VA a vertical shift register, HS a horizontal shift register, IL an interlace circuit, and CS a column switch which is turned on and off in response to outputs from the horizontal shift register. The resolution of such a solid state camera is determined primarily by the number of pixels. It is difficult to increase considerably the number of pixels because of restrictions by manufacturing processes, high aperture rate, driving speed and the like.
In order to improve the horizontal resolution without increasing the number of pixels, an image pickup device of a so-called "pixel displacement type" has been proposed, the construction of which is shown in FIG. 2.
In FIG. 2, three color filters Cy, W and Ye are used, one unit being composed of filters disposed over two lines in a triangular shape. A horizontal scan is effected in units of filters disposed in a triangular shape. Three color signals are outputted onto respective signal lines within the baseband. The misalignment between spacial positions and signal timings is corrected by delay lines provided outside of the device, in the manner as illustrated in FIG. 3. In the Figure, H clocks are shift clocks from the horizontal shift register HS.
Using the obtained signals, the color and luminance signals are calculated by the following equations at a matrix circuit. EQU R=W-Cy EQU B=W-Ye EQU G=Cy+Ye-W EQU Y=Cy+W+Ye
As described above, in order to correct the misalignment between spatial positions and output signal timings, it is necessary to provide delay lines outside the image pickup device. However, if there is a difference in phase and amplification factor of the delay lines, interference signals within the bandwidth of the luminance signal appear on the displayed image. Thus, it is required to use delay lines having high precision phase and amplification factor.
In addition, there arises a problem that it is difficult to use delay lines having the same characteristic because the characteristic varies with each delay line.